Armored face conveyor extendable at head gate end

ABSTRACT

A device is provided for detecting and adjusting the tension of the scraper chain. The device identifies broken chain as it leaves the return sprocket and enters the top race of the conveyor. When detected, the chain can be stopped automatically by the armored face conveyor control system, to avoid the potential for further damage, and warn the operators that repair of the chain is required. 
     The device also provides a conveyor with sliding frames at both ends to allow the conveyor ends to be independently adjusted to each end of the coal block, whilst maintaining good chain tension and control.

BACKGROUND

This disclosure relates to a mechanism to control the position of ascraper chain conveyor and for detection and adjustment of the tensionof a scraper chain of a chain conveyor.

Conveyors, such as armored face conveyors, are part of an integratedlongwall system that also comprises a coal-cutting machine and roofsupports. As the longwall system removes mineral from the mineral blockone strip (web) at a time, the load on the conveyor changes as thecutter moves along the conveyor. The conveyor progressively movesforward one web in order to reposition itself for the next cut.

The mineral being mined is dragged along a top race of the conveyor by acontinuous chain and flight-bar assembly driven by sprockets at each endof the conveyor. More particularly, spaced apart chains, with the flightbars connecting the chains, are typical. At the delivery end, themineral is discharged onto an adjacent conveyor while the continuouschain enters a bottom race where it proceeds to a return end, where areturn end drum or sprocket reverses the direction of the chain.

Armored face conveyors normally operate at a fixed overall length(sprocket centers), but more usually they are fitted with an extendablereturn end frame. The purpose of the extendable return end frame is totake-up slack chain generated during normal operations. The variationsin load and the repositioning of the many parts of the conveying systemresult in changes in chain tensions. To ensure slack chain is notproduced, the movement of the extendable return end frame is sometimesautomatically controlled to maintain a fixed chain tension.

This repeated action involves the repositioning of the many parts thatmake-up the total conveying system. Keeping the equipment inline withthe coal block is difficult, as no direct steering mechanism isavailable with these systems. The operators have to rely on theirexperience by adjusting the relative position of the conveyor to thecoal block to counteract a tendency of the equipment to gradually creepsideways. This inevitably results in face creep with the only correctiveaction available to the operators being to angle the conveyor a fewdegrees off square to the coal block. This is very slow and extremelydifficult to gauge.

In certain operational situations, one of the two chains of the chainand flight bar assembly may get broken on the top race. The remainingchain can then enter the return race with the broken chain. Lowertensions in the bottom race can be contained by the single chain, whichcontinues to the return end and then over the return end sprocket. Ifthe broken chain is not identified on the top race, the result will befailure of the second chain, which is most likely when it approaches thedischarge area. Consequence damage to related equipment can then occur.Failure is followed by prolonged down time to make a repair. Visualidentification of the broken chain is possible, but is unlikely becausethe chain is covered with the mineral being conveyed. Additionally, onmost installations, safety requirements prohibit operators from beingadjacent the return end of the conveyor, which further reduces theopportunity for manual detection.

FIG. 1, which is taken from Bandy U.S. Pat. No. 5,131,528, illustrates aprior art scraper chain conveyor. FIG. 1 illustrates in simple form thevarious conveyor elements necessary for understanding of the conveyorequipment environment. The conveyor apparatus or assembly is showngenerally by the character numeral 10 and includes a drive drum/sprocket12 and an idler or guide drum/sprocket 14 separated by a span of aflexible conveyor 16, illustrated partially in dashed line outline. Asdepicted, the conveyor 16 comprises dual conveyor chains 18 and amultiplicity of spaced flight bars 20 attached to the dual chains 18.During operation of the conveyor assembly, the flight bars 20 pushaggregate material, such as mined coal, along an underlying conveyor pan21. The conveyor assembly 10 is typically positioned juxtaposed to amine wall where a seam of material is being mined for transporting thematerial to one end. The material is then transferred to an auxiliaryconveyor for further disposition.

The drum/sprocket 12 is appropriately coupled to a conveyor drive motor22. Operation of motor 22 causes the sprocket intermeshing with the dualchains 18 to advance the conveyor 16. A pair of sidewalls 24 forming afirst portion of a “split frame” of conveyor assembly 10 serves torotatably support the drum/sprocket 12. The sidewalls 24 are illustratedas being telescopingly engaged with a second pair of sidewalls 26forming a second portion of the frame and, collectively with sidewalls24, comprise the aforementioned split frame. The telescoping joint,indicated generally by character numeral 48, permits the frame portionsto be moved relative to one another.

The idler drum/sprocket 14 is appropriately mounted for rotary movementbetween sidewalls 26. Relative movement at the joint 48 between theadjacent sidewalls 24 and 26 thus causes the distance span between thedrum/sprockets 12 and 14 to vary accordingly. The dual conveyor chains18 can be provided with increased or reduced tension depending upon thedirection of adjusting movement of the supporting drum/sprockets withrespect to each other. To provide this relative movement, assembly 10has a tensioning means in the form of a pair of hydraulic cylinders 28and 30, each mounted on and secured to an adjacent sidewall 26. In otherembodiments (not shown), only a single hydraulic cylinder can be used.The cylinders have respective pistons 32 and 34, each of which isoperatively coupled to a sidewall 24 in any known and expedient manner.

Movement of the pistons 32 and 34 causes the first portion of theconveyor 16 represented by the side walls 24 to move longitudinallyrelative to the second portion and side walls 26, thus relaxing ortensioning the chain 18, as desired. Control of movement of pistons 32and 34 is affected by a conventional hydraulic tensioning controlcircuitry, depicted generally by numeral 40 in FIG. 1.

As stated above, a certain amount of tensioning of conveyor chain 18 isessential for the proper and efficient operation of the conveyorassembly 10. Too little tension may cause the conveyor chain to ride upthe teeth of the sprockets, and even eventually, under severeconditions, become disengaged. Conversely, too much tension may causethe conveyor components to be over stressed, increasing the risk ofmechanical failure in the various parts of the conveyor apparatus.

FIG. 2, which is taken from Weigel et al U.S. Pat. No. 7,117,989,illustrates a prior art mechanism for controlling the tension in ascraper chain in a conveyor. FIG. 2 shows a tensionable return station,marked as 51, which forms the auxiliary drive of a face conveyor, and onwhich a spoked chain wheel 52 is located, which may be powered by drives(not shown).

All channel sections 70 and machine frame 51 and, where applicable, anyintermediate or transitional channels located between them, have a toprace 54 A and a bottom race 54 B. In top race 54 A the material to beconveyed, such as coal, is transported by means of scrapers 20 as far asthe main drive, and in bottom race 54 B the scrapers run back to theauxiliary drive. The constantly changing load conditions in the top racecause the tension in the top race and bottom race sections of conveyor16 to vary.

In order to detect the tension of conveyor 16, a sensor, indicatedoverall by 60, is located on the frame of return station 51, which formsthe auxiliary drive. The sensor has a sliding body or sensor body 62with a curved sliding surface 61, which is coupled with a shaft 63 suchthat it cannot be turned, said shaft reaching obliquely over theconveying trough and return trough for scraper conveyor 16 in top race54 A of machine frame 51 of the chain conveyor. Shaft 63 is supported inbearing blocks 64, one of which is indicated schematically at the rearside face of return station 51. The weight of sensor body 62 causes itssliding surface 61 to be directly in contact with the upper face of ascraper 20 or with the upper face of vertical chain links 57 in the areaof the measuring zone. At the same time, shaft 63, supported in bearingblocks 64 such that it can swivel, forms a measuring shaft, and by meansof shaft encoder 65 the relative position of measuring shaft 63 and thusalso the relative position or swiveled position of sensor body 62rigidly coupled with it may be detected and transmitted to theevaluation and control unit 72 via signal line 71. Depending on themeasurement signal of shaft encoder 65, evaluation and control unit 72then activates tensioning drive 55 of return station 51 via signal line75.

In an extensive zone within top race 54 A of return station 51, referredto below as the measurement zone, and extending between points 67 and 68in the drawing marked with double arrows, scraper conveyor 16 hasvertical play. In other words, between point 67 and point 68 along thetrack in top race 54 A, conveyor 16 can essentially move freely in avertical direction, i.e. perpendicularly to the bottom of top race 73,74.

In the embodiment shown, the scraper chain is running with optimumtension, i.e. some chain links in the measuring zone are slightly liftedaway from the bottom of top race 74. When the chain is dangling, on theother hand, chain links 57, 58 and scrapers 59 within the area of themeasuring zone and in the area of the machine frame are in contact atevery point with the bottom of top race 73 or 74 of return station 51,and sensor body 62 is at its largest downwards deflection. This state isdetected by evaluation and control device 72 and tensioning drive 55 isextended. If the tension of scraper conveyor 16 increases, vertical andhorizontal chain links 57, 58 together with scrapers 59 of scraperconveyor 16 may move even higher in the measuring zone, due to theabsence of restrictive guidance and the existing vertical play (67 or68), which causes sensor body 62 to be swiveled clockwise and thisdeflection to be detected by shaft encoder 65 and transmitted toevaluation and control device 72 as a measurement signal. If the chainreaches a preset tension corresponding to that of a tight chain, this isdetected directly by shaft encoder 65 as a result of the greaterdeflection of sensor body 62, and evaluation and control device 72 thenactivates tensioning drive 55, in some cases via a closed-loop controlalgorithm, through signal line 75 such that tensioning cylinder 56 isretracted in order to reduce the tension in scraper conveyor 16.

Other mechanisms for monitoring chain tension include U.S. Pat. Nos.5,505,293, and 4,657,131.

SUMMARY

This disclosure takes as its starting point the typical longwallconveyor described above where the delivery end is fixed and the returnend has a telescopic sliding frame. The principal object of thisdisclosure is to provide a device for detecting and adjusting thetension of the scraper chain, which determines the tension reliably andsimply. Another object of this disclosure is to provide such a devicethat reliably senses chain tension while at the same time not adverselyaffecting the chain path.

This disclosure also provides a means of identifying broken chain as itleaves the return sprocket and enters the top race of the conveyor. Whendetected, the chain can be stopped automatically by the armored faceconveyor control system, to avoid the potential for further damage, andwarn the operators that repair of the chain is required.

Another principal object of this disclosure is to provide sliding framesat both ends of the conveyor to allow the conveyor ends to beindependently adjusted to each end of the coal block, whilst maintaininggood chain tension and control.

Providing the delivery and return end frames with a telescopic sectionaddresses the problem of face creep by allowing the operator to quicklyadjust the position of both ends of the conveyor, thus offsetting theeffects of face creep. This is particularly critical on conventional enddischarge conveyor systems, where the correct relationship between thelongwall discharge conveyor and an auxiliary cross conveyor (beam stageloader) must be maintained. This problem becomes even more criticalwhere there are two longwall conveyors operating side by side, which isoften the case with sub-level caving or longwall to coal caving.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a plan view of a prior art delivery discharge end scraperchain conveyor arrangement.

FIG. 2 is a schematic view of a prior art tension sensor for detectingand tensioning a scraper chain.

FIG. 3 is a plan view of an improved tension sensor.

FIG. 4 is a perspective view of an alternate embodiment of the tensionsensor shown in FIG. 3.

FIG. 5 is a perspective view of the tension sensor shown in FIG. 4, asmounted at the return end of a conveyor.

FIG. 6 is a perspective view of a load cell used in the tension sensorof FIGS. 4 and 5.

FIG. 7 is a schematic top view of the chain, two tension sensors and atension control.

FIG. 8 is a top view of a conveyor and a secondary or auxiliaryconveyor.

FIG. 9 is a side view of the conveyor and auxiliary conveyor shown inFIG. 8.

FIG. 10 is a top view of a double conveyor system.

Before one embodiment of the disclosure is explained in detail, it is tobe understood that the disclosure is not limited in its application tothe details of the construction and the arrangements of components setforth in the following description or illustrated in the drawings. Thedisclosure is capable of other embodiments and of being practiced orbeing carried out in various ways. Also, it is to be understood that thephraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. Use of “including”and “comprising” and variations thereof as used herein is meant toencompass the items listed thereafter and equivalents thereof as well asadditional items. Use of “consisting of” and variations thereof as usedherein is meant to encompass only the items listed thereafter andequivalents thereof. Further, it is to be understood that such terms as“forward”, “rearward”, “left”, “right”, “upward” and “downward”, etc.,are words of convenience and are not to be construed as limiting terms.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 3 illustrates an improved version of the tension sensing means 60shown in FIG. 2. Conventionally, to allow for optimum use of the lengthof the tailgate or return end or station 51, a wear strip 101 isinstalled to guide the conveyor 16 down to the track or race 54 A level.The tensioning means, or tension sensor 104, of FIG. 3, comprises a wearstrip 101 including a wear plate 108 that contacts the top surface ofthe conveyor 16.

The wear plate 108 is supported by a wear strip support 112, and thewear plate 108 is connected to the wear strip support 112 by a pin 116at one end and a load-sensing pin 120 at the other end. The wear plate108 engages the top surface of the conveyor 16, and changes the path ortrajectory of the movement of the conveyor 16. This contact and changein direction of the conveyor 16 causes a force to be applied on the wearplate 108. The load-sensing pin 120 that connects the wear plate 108 tothe wear strip support 112 senses this force. The output from theload-sensing pin 120 is then be used to determine the tension of theconveyor 16, and to adjust the tension, as needed, using anyconventional chain tensioning system, such as the joint 48 and pistons32 and 34 and circuitry of FIG. 1.

An alternate and preferred embodiment 124 of the tension sensor isillustrated in FIG. 4. In FIG. 4, a load cell 128 is located between awear plate 132 and a wear strip support 136. The load cell 128, which isillustrated in FIG. 6, is a cylinder including a plurality of spacedapart passageways 130 through the cylinder. Within the passageways areload sensors (not shown), which measure the compression force on theload cell 128. By placing the load cell 128 between the wear plate 132and the wear strip support 136, the load cell 128 responds to the forceapplied to the wear plate 132 by the conveyor 16. In order to provideredundancy, as shown in the preferred embodiment illustrated in FIG. 4,two spaced apart load cells 128 are placed between the wear plate 132and the wear strip support 136. More particularly, the wear stripsupport 136 includes a cavity 138 that receives the load cells 128, andthe wear plate 132 is connected to the wear strip support 136 by meansof a screw 140.

FIG. 5 illustrates a perspective view of the load sensor 124 mounted onthe conveyor apparatus 10 at the return end 51. As shown, the cavity 138receiving the load cells 128 can be formed by a plate 142 secured to thewear strip support 36. This provides ready access to the load cells 128from adjacent the conveyor apparatus 10, without the need forsignificant disassembly of conveyor parts. This thus permits readyaccess and repair of the tension sensor 124, when the need arises.

The disclosure also illustrates, in FIG. 7, the providing of two suchtension sensors on such a conveyor apparatus 10. More particularly, inthis embodiment, the conveyor 16 includes the two spaced apart chains18, and the plurality of flights or flight bars 20 that are connectedand spaced apart but between the two chains 18. Each conveyor flight 20has a first end and a second end. Each flight bar end is spaced apartfrom its respective adjacent chain. A tension sensor, such as thetension sensor illustrated in FIGS. 2, 3 and 4 above, is provided in arespective wear strip for each one of the two conveyor chains 18. Eachtension sensor 124 is electrically connected via a line 154 to acomparator 158.

In the preferred embodiment, as illustrated in FIG. 7, the part of theconveyor that contacts the tension sensor 124 is the end or tip of theflight bar 20. In other embodiments, not shown, a tension sensor 124 canbe placed above each of the chains, instead of the flight tips. The tipof the flight bar 20 will only contact the wear strip intermittently. Asa result, the tension sensor 124 will only produce intermittent signals.

To eliminate transient load spikes and to allow for the odd missingflight bar 20, the tension sensor 124 collects a rolling average readingover 20 or so flight bars. As each flight bar tip passes along the loadsensor, even at a constant chain tension, the signal varies due to thechanging geometry of the system. The tension sensor 124 records the peaksignal value as each flight bar 20 passes over the wear plate 132. Ifthe rolling average peak reading is too low, then the tension meansmoves the joint 48 to stretch the chain, or vice versa. The tensionmeans is initialized by establishing a required peak signal value bystopping the conveyor with a flight bar under the sensor, fitting atemporary load transducer to the chain itself, and then moving the joint48 to tension the static chain. When the chain is at the requiredtension, the tension sensor 124 stores the signal, and it is this signalvalue that the tension sensor 124 maintains while the conveyor isrunning.

The above overview is a simplified version of the sensor signalmanagement system, and applies to steady chain load increase or decreaseduring the coal cutting cycle. The tension sensor 124 must also dealwith special events such as starting a full conveyor or the rapidunloading of a conveyor, like when the shearer stops cutting. Collectinga rolling average signal cannot respond quickly enough to deal withthese events, so advance action must be taken. For example, the sprocketis extended to significantly stretch the chain before loaded conveyorstartup to prevent generation of slack chain.

In the event of a chain break, the tension in the two chains 18 will bedifferent. The outputs of the tension sensors 124 are compared by acomparing means, comparator 158, and in the event of a significantdifference, the operation of the conveying apparatus 10 can be stoppedso the broken chain can be repaired. In the preferred embodiment, thetension sensors 124 are provided adjacent the top race of the return endof the conveyor apparatus. If additional sensors or sensing of thetension at other locations in the conveying apparatus is desired, othertension sensors 124, in other locations, can be used. The use of the twotension sensors 124 is also beneficial, for the output from the tensionsensors 124 can be averaged to produce a more accurate indication ofoverall conveyor tension. The comparator 158 forms a part of the chaintensioning system such as the joint 48 and pistons 32 and 34 andcircuitry of FIG. 1.

As illustrated in FIG. 8, an auxiliary or secondary conveyor 200 islocated at one end of a conveyor apparatus 210. The material on theconveyor 16 leaves the conveyor and is dumped onto the auxiliaryconveyor 200. During operation of the conveyor apparatus 210, thelocation of the conveyor apparatus 210 may move relative to the locationof the auxiliary conveyor 200. Currently, operators need to make variousadjustments in order to try to accommodate such movement. This canresult in difficulty maintaining conveyor operation.

The improvement in this disclosure is, in order to accommodate somemovement of the conveyor apparatus 210 relative to the auxiliaryconveyor 200, the conveyor apparatus frame accommodates sliding movementat both ends. At one end, the sliding movement adjusts the tension ofthe conveyor 16, and sliding movement at the other end accommodatesmovement of the conveyor apparatus 210 relative to the auxiliaryconveyor 200. If the conveyor apparatus 210 moves relative to theauxiliary conveyor 200, an operator can move the sliding end of theconveyor 210 adjacent the auxiliary conveyor 200. Movement of thesliding end of the conveyor 210 can also be occasioned by the use oftensioning means, as described hereinafter, as used on the tensioningend 51 of the conveyor 16. Only in this instance, the movement is notintended to effect the tension of the conveyor 16, but the location ofthe end of the conveyor apparatus 210 relative to the auxiliary conveyor200. When movement at this end of the conveyor occurs, the chain tensiondoes change, so the other end of the conveyor apparatus 210 is adjustedby the automatic tensioning means to return the conveyor 16 back to theappropriate tension. Movement of the sliding end of the conveyor 210adjacent the auxiliary conveyor 200 much overcome the maximum workingchain tensions (which are at there highest as these top chains reachthis frame; plus significant sliding friction due to the typical largesize and weight of the Main gate equipment.

More particularly, a driven drum/sprocket 312 is appropriately coupledto a conveyor drive motor 322. Operation of motor 322 causes thesprocket intermeshing with the dual chains 18 to advance the conveyor16. More particularly, as illustrated in FIGS. 8 and 11, in addition tothe hydraulic pistons 32 and 34 spanning the joint 48 at the return end51, a pair of sidewalls 324 forming a first portion of a “split frame”of the main gate end of the conveyor apparatus serves to rotatablysupport the drum/sprocket 312. The sidewalls 324 are illustrated asbeing telescopingly engaged with a second pair of sidewalls 326 forminga second portion of the frame and, which collectively with sidewalls324, comprise the aforementioned split frame. The telescoping joint,indicated generally by character numeral 348, permits the frame portionsto be moved relative to one another.

Relative movement at the joint 348 between the adjacent sidewalls 324and 326 thus causes the distance span between the drum/sprockets 312 and14 to vary accordingly. The conveyor 16 can be provided with increasedor reduced tension depending upon the direction of adjusting movement ofthe supporting drum/sprockets with respect to each other. To providethis relative movement, the conveyor assembly 310 has a pair ofhydraulic cylinders 328 and 330, each mounted on and secured to anadjacent sidewall 326. The cylinders have respective pistons 332 and334, each of which is operatively coupled to a sidewall 324 in any knownand expedient manner.

The location of the conveyor apparatus relative to the auxiliaryconveyor is further illustrated in FIG. 9. If desired, in lieu ofoperator correction of the location of the conveyor apparatus, theconveyor apparatus can be physically connected by a bar 352 to theauxiliary conveyor. In this instance, tension is maintained at this endof the conveyor by some tensioning means, such as the tensioning meanspreviously described. But in order to accommodate some movement in theevent the auxiliary conveyor and main conveyor change location, either ahydraulic accumulator (now shown), or some relief valve (now shown) mustbe provided in the hydraulic tensioning means in order to allow for themovement of this sliding end of the conveyor apparatus 210. When thisend of the conveyor apparatus 210 adjusts by movement of the auxiliaryconveyor 200, then tension is corrected, as described before, by thereturn end 51.

The problem of conveyor apparatus movement relative to the auxiliaryconveyor is especially relevant where a pair of conveyor apparatus isused. As illustrated in FIGS. 10 A and 10 B, it is known to use oneconveyor adjacent a coal face, and a second conveyor apparatus behindthe roof supports to collect coal that falls from the longwall roof asthe longwall advances. In this instance, the double sliding frame endswould be used with both conveyor apparatus.

Additionally the frame-sliding 48 and 348 can be adjusted to correctlyalign the conveyor end with both edges of the coal block, moving boththe return end frame and delivery end frame at the same time to maintaincorrect chain tension during this adjustment. This would not be a normalrequirement or mode of operation as the position of the Return End Frameto coal block is less critical in most cases.

This aspect of the disclosure thus has the following benefits. Manual orautomatic control of the delivery end frame sliding module makes fineadjustments for optimum discharge of material from the extendablelongwall armored face conveyor to the cross beam stage loader conveyor.

Since the changes in the overall length of the conveyor, as a result ofadjusting the delivery end sliding frame module will change the chaintension, adjustments must be in small increments and effected slowly togive the automatic chain tensioning system time to react. At all timesit is the automatic chain tensioning system that controls and maintainscorrect chain tension, not the adjustment of the delivery end framemodule.

Various other features and advantages of the disclosure will be apparentfrom the following claims.

The invention claimed is:
 1. A conveyor apparatus including a firstconveyor, a frame having a return frame portion, an intermediate frameportion adjacent the return frame portion, and a drive frame portionadjacent the intermediate frame portion, the return and intermediateframe portions being movable with respect to each other generally alonga longitudinal axis of the conveyor, the drive frame portion having adelivery end and being movable with respect to the intermediate frameportion generally along the longitudinal axis of the first conveyor, areturn sprocket mounted on said return frame portion for supporting oneend of said first conveyor, a drive sprocket mounted on said drive frameportion for supporting and driving the other end of said first conveyor,a first actuator having a first end coupled to the drive frame portionand a second end coupled to the intermediate frame portion to move saiddrive sprocket and said intermediate frame portion with respect to eachother, a second actuator having a first end coupled to the return frameportion and a second end coupled to the intermediate frame portion tomove the return sprocket relative to the drive sprocket, an auxiliaryconveyor receiving material discharged by the first conveyor, theauxiliary conveyor being positioned adjacent the delivery end of thefirst conveyor, the frame portion proximate the delivery end of thefirst conveyor being coupled to and movable with the auxiliary conveyoralong the longitudinal axis of the first conveyor, and a control systemoperable to sense a tension of the first conveyor, operate the firstactuator and the second actuator to adjust a tension in the firstconveyor, operate at least one of the first actuator and the secondactuator to maintain a position of the delivery end of the firstconveyor relative to the auxiliary conveyor during the advance of thefirst conveyor, and operate the first actuator and the second actuatorto maintain a position of the drive sprocket relative to the returnsprocket in response to movement of one of the return frame portion andthe drive frame portion.
 2. A conveyor apparatus according to claim 1,wherein said drive frame portion is free to move relative to saidintermediate frame portion.
 3. A conveyor apparatus according to claim1, further comprising a drive system including a motor for operating thedrive sprocket, the drive system being supported on the drive frameportion and movable with the drive sprocket relative to the intermediateframe portion.
 4. A conveyor apparatus according to claim 1, wherein thefirst actuator includes a hydraulic cylinder coupled between the driveframe portion and the intermediate frame portion.
 5. A conveyorapparatus according to claim 1, wherein the first actuator moves thedrive frame portion in a telescoping manner relative to the intermediateframe portion.
 6. A conveyor apparatus according to claim 1, wherein theauxiliary conveyor is positioned proximate the drive frame portion.
 7. Aconveyor apparatus including a first conveyor including a delivery end,a frame having a return frame portion, an intermediate frame portionadjacent the return frame portion, and a drive frame portion adjacentthe intermediate frame portion, the return and intermediate frameportions being movable with respect to each other, the drive frameportion being freely movable with respect to the intermediate frameportion, one of the return frame portion and the drive frame portionbeing positioned proximate the delivery end, a return sprocket mountedon said return frame portion for supporting one end of said firstconveyor, a drive sprocket mounted on said drive frame portion forsupporting and driving the other end of said first conveyor, a firstactuator mounted on said frame and spanning the return and intermediateframe portions to move said return and intermediate frame portions withrespect to each other to move said return sprocket and said intermediateframe portion with respect to each other generally parallel to alongitudinal axis of the first conveyor, an auxiliary conveyor receivingmaterial discharged by the first conveyor, the auxiliary conveyor beingpositioned adjacent the delivery end of the first conveyor and definingan auxiliary conveyor axis that is positioned at an angle relative tothe longitudinal axis of the first conveyor, a second actuator mountedon said frame and spanning the drive and intermediate frame portions ofsaid frame to move said drive sprocket and intermediate frame portionswith respect to each other generally parallel to the longitudinal axis,and a control system operable to sense a tension of the first conveyor,operate at least one of the first actuator and the second actuator toadjust a tension in the first conveyor, operate at least one of thefirst actuator and the second actuator to maintain a position of thedelivery end of the first conveyor relative to the auxiliary conveyorduring the advance of the first conveyor, and operate the first actuatorand the second actuator to maintain a position of the drive sprocketrelative to the return sprocket in response to movement of one of thereturn frame portion and the drive frame portion during advance of theconveyor.
 8. A conveyor apparatus according to claim 7, furthercomprising a motor for driving the drive sprocket, the motor beingsupported on the drive frame portion and movable with the drive sprocketrelative to the intermediate frame portion.
 9. A conveyor apparatusaccording to claim 7, wherein the second actuator includes a hydrauliccylinder.
 10. A conveyor apparatus according to claim 7, wherein thesecond actuator slidably moves the drive frame portion relative to theintermediate frame portion.
 11. A conveyor apparatus according to claim7, wherein the delivery end is formed on the drive frame portion and theauxiliary conveyor is positioned proximate the drive frame portion. 12.A conveyor apparatus according to claim 7, wherein the frame portionproximate the delivery end of the first conveyor is coupled to andmovable with the auxiliary conveyor along the longitudinal axis of thefirst conveyor.
 13. A conveyor apparatus for a longwall system forextracting material from a mine wall, the conveyor apparatus comprising:a first conveyor including a first end and a second end and defining aconveyor axis therebetween and extending in a direction substantiallyparallel to the mine wall, a frame including a return portion, anintermediate portion, and a drive portion, the intermediate portionbeing positioned between the return portion and the drive portion, thereturn and intermediate portions being movable with respect to eachother, and the drive portion being movable with respect to theintermediate portion in a direction generally parallel to the conveyoraxis, a return sprocket mounted on the return portion for supporting thefirst end of the first conveyor, a drive sprocket mounted on the driveportion for supporting and driving the second end of the first conveyor,a first actuator coupled between the drive and intermediate portions tomove the drive and intermediate portions with respect to each othergenerally along the conveyor axis, a second actuator coupled between thereturn and intermediate portions to move the return and intermediateportions with respect to each other generally along the conveyor axis,an auxiliary conveyor receiving material discharged by the firstconveyor, the auxiliary conveyor being positioned adjacent one of thefirst end and the second end along the conveyor axis, and a controlsystem operable to sense a tension of the first conveyor, operate atleast one of the first actuator and the second actuator to adjust atension in the first conveyor by changing a distance between the firstsprocket and the second sprocket, operate at least one of the firstactuator and the second actuator to maintain a position of the deliveryend of the first conveyor relative to the auxiliary conveyor duringadvance of the first conveyor, and operate at least one of the firstactuator and the second actuator to maintain a position of the drivesprocket relative to the return sprocket in response to movement of oneof the return frame portion and the drive frame portion.
 14. A conveyorapparatus according to claim 13, wherein the first actuator slidablymoves the drive frame portion relative to the intermediate frameportion.
 15. A conveyor apparatus according to claim 13, wherein thefirst actuator includes a pair of hydraulic cylinders, each cylinderhaving a first end coupled to the drive portion and a second end coupledto the intermediate portion.
 16. A conveyor apparatus according to claim13, wherein the auxiliary conveyor is positioned adjacent the second endof the first conveyor.
 17. A conveyor apparatus according to claim 13,wherein the frame portion proximate the delivery end of the firstconveyor is coupled to and movable with the auxiliary conveyor along theconveyor axis.
 18. A method of operating a face conveyor, the methodcomprising: providing a face conveyor defining a delivery end andsupported by a first sprocket and a second sprocket, the first sprocketbeing supported by a first frame portion, the second sprocket beingsupported by a second frame portion, an intermediate portion beingpositioned between the first frame portion and the second frame portion;providing an auxiliary conveyor for receiving material discharged fromthe face conveyor, the auxiliary conveyor being positioned proximate thedelivery end; sensing a tension in the face conveyor; moving the firstframe portion relative to the second frame portion to set a tension ofthe face conveyor at a predetermined level; moving at least one of thefirst frame portion and the second frame portion to maintain a positionof the delivery end of the face conveyor relative to the auxiliaryconveyor as the face conveyor advances, and moving one of the firstframe portion and the second frame portion in response to movement ofthe other of the first frame portion and the second frame portion tomaintain a predetermined distance between the first sprocket and thesecond sprocket.
 19. A method according to claim 18, wherein moving oneof the first frame portion and the second frame portion includesmaintaining one of the first sprocket and the second sprocket at apredetermined position relative to the auxiliary conveyor.